I've been looking into Lua as a powerful AI and effect scripting option. However, I have been so far unable to find a reasonable editor and compiler (for free, mind you). Any idea where I might find a usable Lua editor/executer?

eh? Your favorite text editor (as long as it's not Xcode) should have a syntax hilighting module for lua; the lua interpreter is free from lua.org.

Oh. Sweet, thank you.

TextMate is $50 and is the best IDE ever for everything that isn't Cocoa. I think it has a free Lua plug-in. I use it for HTML/CSS, Java, Python, and general text editing. Everything is integrated, including keyboard shortcuts, etc.